The Driver’s Seat by Muriel Spark

Lise has been driven to distraction by working in the same accountants' office for sixteen years. So she leaves everything behind her, transforms herself into a laughing, garishly-dressed temptress and flies abroad on the holiday of a lifetime.

But her search for adventure, sex and new experiences takes on a far darker significance as she heads on a journey of self-destruction. Infinity and eternity attend Lise's last terrible day in an unnamed southern city, as she meets her fate.